The invention discloses a method applied to efficient suspension liquid fertilizer containing fulvic acid for lettuce. The suspension liquid fertilizer includes, by weight, 10-25 parts of fulvic acid, 35-50 parts of major element, 1-10 parts of medium element, 0.2-3 parts of trace element, 0-3 parts of functional substance, 3-5 parts of suspended aid, 2-12 parts of a composite chelating agent, 0-1 parts of a defoaming agent, 0-1 parts of solution stabilizer, and a thickener. The preparation method comprises the steps of: adding water, potassium humate, nitrogen fertilizer and potassium fertilizer into a reactor A, and conducting high-speed stirring to prepare a saturated mother liquor; adding water, phosphate fertilizer, trace element material, a dispersing agent, a filler and partial defoaming agent into a reactor B, conducting high-speed stirring and grinding for the formation of a solid-liquid mixture; mixing the saturated mother liquor and solid-liquid the mixture, adding a thickening agent, residual defoaming agent and an anti-freezer, and emulsifying to prepare a suspension liquid fertilizer. The invention has the advantages of high total nutrient content, no layering or deposition, and realization of long distance transportation.